JP2014111926A - Muffler and engine work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a muffler which is made compact by devising the shape and arrangement of a connection duct connecting an exhaust port to an expansion chamber.SOLUTION: A branch duct which branches off from a connection duct 21 is formed by connecting the connection duct 21 in a substantially channel shape in side view to an exhaust port of an engine, forming a branch part (opening 21d) halfway in the connection duct 21, and joining a curved branch member 30 to a curved cut-out part 41c formed on the housing 41. An end of the branch duct is closed with a closing part 44. The connection duct 21 is arranged inside the housing 41 in contact and passes through a through hole 35c of a partition plate 35 to be open in a first expansion chamber 40a. The connection duct 21 has an opening part 21c, and is soldered inside the housing 41 so as to constitute a duct. The connection duct 21 is arranged inside the housing 41 to make an expansion chamber formed of the housing 41 large.

Description

  The present invention relates to a muffler suitable mainly for use in engine working machines such as a brush cutter, a chain saw, a cutter, and a blower. In particular, the exhaust gas is reduced and the output characteristics are improved. The present invention also relates to a muffler capable of improving accuracy and an engine working machine using the muffler.

  2. Description of the Related Art Two-cycle engines are widely used in portable engine working machines that are required to be small, light, and have high output. The two-cycle engine has a problem of low output and high exhaust gas due to the blowout of fresh air to the exhaust port during exhaust and scavenging strokes. To prevent this, the number and shape of the scavenging ports or exhaust ports are devised. Alternatively, a layered scavenging system in which air is led is known. In Patent Document 1, it is possible to reliably obtain an exhaust pressure pulsation effect by connecting a branch pipe line where one end is closed and the other open end part is connected to a connection pipe extending from the exhaust port. A muffler is disclosed. Further, the muffler of Patent Document 1 has a connection port with a connection port curved in a U-shape so as to face the crankcase side, and the expansion chamber 40 is formed in an engine block composed of a cylinder and a crankcase and in a curved space between the connection pipelines. The size of the muffler is reduced while increasing the expansion chamber capacity.

JP 2012-202293 A

  Usually, the pressure pulsation type muffler provided in a hand-held engine tool is often limited in height, width, and depth from the viewpoint of product miniaturization and the configuration of peripheral parts. For this reason, in the technique of Patent Document 1, the expansion chamber is disposed between the connection pipe line and the engine, the expansion chamber is formed along the shape of the engine, and the connection pipe line is adjacent to the outside of the expansion chamber. By doing so, we realized a muffler that can secure the length of the connecting pipeline sufficiently in the space where the height, width, and depth are limited. In addition, a low exhaust gas due to pressure pulsation of exhaust gas by connecting a U-shaped branch pipe (branch pipe) with a branch portion provided in the middle of the connection pipe and one end closed from the branch, A muffler that can achieve a high output effect has been realized. However, if the expansion chamber is further expanded outside in order to further improve the exhaust pressure pulsation efficiency, the expansion is hindered by the connecting pipe line provided along the outside of the expansion chamber. Also, if you try to expand the expansion chamber only in the part other than the connection line so as to avoid the connection line, the width of the engine work machine becomes large, the shape of the muffler housing becomes complicated, and it is cheaper by pressing. If it becomes impossible to manufacture correctly, it will lead to an increase in manufacturing cost.

  The present invention has been made in view of the above background, and an object of the present invention is to provide a muffler in which the capacity of the expansion chamber is ensured by successfully routing a connecting pipe that connects the exhaust outlet of the cylinder and the expansion chamber inlet of the muffler. It is in.

  Another object of the present invention is to effectively connect the connecting pipe line connecting the exhaust outlet of the cylinder and the expansion chamber inlet of the muffler, and further connect the U-shaped branch pipe to the connecting pipe to increase the effect of pressure pulsation. The aim is to provide an enhanced muffler.

  It is still another object of the present invention to provide a muffler with improved assembly structure, which can be manufactured at low cost and has high reliability.

  The characteristics of representative ones of the inventions disclosed in the present application will be described as follows.

  According to one aspect of the present invention, there is provided a muffler having a front housing and a rear housing constituting the outer wall of the expansion chamber, and fixed to an engine cylinder. The rear housing has an exhaust port formed in the cylinder. An opening to be connected was provided, and a connecting pipe routed from the opening along the inner wall of the front housing to open into the expansion chamber was provided. If the connection pipe is formed in a substantially U shape so that the end opening to the expansion chamber faces the crankcase side of the engine, the connection pipe can be reduced in size. In addition, a partition plate is provided between the front housing and the rear housing, and the connection line passes through the second expansion chamber so that the expansion chamber is divided into a first expansion chamber on the rear housing side and a second expansion chamber on the front housing side. Extending into the first expansion chamber. The volume ratio of the first expansion chamber and the second expansion chamber can be set so that the first expansion chamber: the second expansion chamber = 3: 7 to 7: 3. It is preferable to set it to be larger than the volume of the expansion chamber.

  According to another feature of the present invention, the partition plate is provided with an opening from the first expansion chamber to the second expansion chamber, and a through hole or notch that allows the connecting pipe to pass therethrough. A part of the surface of the connection pipe line facing the inner wall of the front housing is open, and the opening is closed by fixing the armature pipe line so that the opening touches the inner wall of the front housing. A branch part is provided in the middle of the connecting pipe, and a branch pipe having one end connected to the branch part and the other end closed is formed in the branch part. The branch pipe line is piped along a split surface between the front housing and the rear housing, and is formed by joining a curved branch member to a curved cutout formed in the front housing, for example.

  According to another feature of the invention, the branch conduit is a convex member that follows the shape of the cutout, and the front housing is formed with a closing portion that closes the other end of the branch conduit. Burring is made around the cutout portion of the front housing, and the branch member is held by the burring. The branch member is formed by pressing a flat plate. An exhaust port is provided in the front housing, and the exhaust gas may be configured to be discharged downward through the exhaust port on the side opposite to the engine.

  According to another feature of the present invention, a part of the surface of the front housing facing the connecting pipe is open, and the opening of the front housing is fixed by the outer wall of the connecting pipe by fixing the connecting pipe to the housing. I tried to close it. With this configuration, brazing, arc welding, and the like can be performed from the outside of the front housing. Further, a flange is connected to the connection pipe, and the flange is fixed to the cylinder with a screw so as to contact the rear housing. At this time, a collar may be interposed between the flange and the front housing, and the fastening screw may be passed through from the outside of the front housing. Furthermore, a branch part is provided in the middle of the connection pipe line, and an independent branch pipe line having one end connected to the branch part and the other end closed is connected to the branch part. The branch pipe is formed by joining at least two divided members on a plane parallel to the axial direction, and the front housing is provided with a convex outer wall adjacent to the outer wall of the branch pipe. It is fixed by welding or brazing at a plurality of locations in the vicinity of the connection, in the middle of the length of the branch pipe, and in the vicinity of the closed end.

According to the present invention, since the connecting pipe is provided along the inner wall of the front housing from the opening and opened into the expansion chamber, the connecting pipe is provided in a space limited in height, width, and depth. A muffler capable of ensuring a sufficient length of the connecting pipe line can be realized.
According to the present invention, the connection pipe line is formed in a substantially U shape so that the other end connected to the expansion chamber faces the crankcase side of the engine, so that the connection pipe line is connected to the muffler directly attached to the engine cylinder. A sufficient length of the pipeline can be secured.
According to the present invention, a partition plate is provided between the front housing and the rear housing, the expansion chamber is divided into a first expansion chamber on the rear housing side and a second expansion chamber on the front housing side, and the volume of the first expansion chamber is further increased. Since the volume of the second expansion chamber is larger than that of the second expansion chamber, a plurality of expansion chambers can be provided in the downsized muffler, and at the same time, the silencing effect and the exhaust efficiency can be improved.
According to the present invention, the partition plate is provided with the opening from the first expansion chamber to the second expansion chamber and the through hole or notch that penetrates the connecting pipe line. Connection pipes can be arranged efficiently.
According to the present invention, a part of the surface of the connection pipe line facing the inner wall of the front housing is opened, and the armature pipe line is fixed so that the opening is in contact with the inner wall of the front housing. The connection pipe line can be formed using the portion, and weight reduction can be achieved. Further, since the inner wall of the housing and the outer wall of the connecting pipe line are made common, it is possible to prevent the generation of resonance sound when the two plate members face each other. As a similar effect, a part of the surface of the front housing facing the connection pipe line is open, and the connection pipe line may be fixed to the front housing so that the opening is closed by the outer wall of the connection pipe line. .
According to the present invention, a branch portion is provided in the middle of the connecting pipe, and a branch pipe having one end connected to the branch and closed at the other end is formed in the branch. You can definitely get it. Further, by simply changing the length and the cross-sectional area of the connection pipe line and the branch pipe line, it becomes possible to apply to the synchronized rotational speed of pulsation and different engine displacements, and the common use of the expansion chamber can be promoted.

According to the present invention, since the branch pipe is piped along the split surface of the front housing and the rear housing, the fixing member can be saved and firmly fixed by fixing the branch pipe using the split surface. .
According to the present invention, the branch pipe is formed by joining a branch member, which is a separate member, to a curved cutout formed in the front housing. Can be realized at low cost.
According to the present invention, the branch pipe is a convex member that follows the shape of the cut-out portion, and the front housing is formed with a closing portion that closes the other end of the branch pipe. A closed branch line can be realized.
According to the present invention, since the burring is made around the cutout portion of the front housing and the branch member is held by the burring, the front housing can be easily manufactured by metal pressing and the branch member can be stably held. Can do.
According to the present invention, since the branch member is formed by pressing a flat plate, almost all the members of the muffler can be realized by pressing and brazing.
According to the present invention, the exhaust port is provided on the front housing side, and the exhaust gas is discharged downward on the side opposite to the engine. Therefore, when the engine working machine with the muffler of the present invention is realized, the worker Against the exhaust gas.
According to the present invention, the branch pipe is formed by joining at least two members, so that the branch pipe can be easily manufactured. Moreover, since the front housing is provided with a convex outer wall adjacent to the outer wall of the branch pipe, the branch pipe can be firmly fixed. Also, the connecting pipe and the branch pipe are joined by welding or brazing in the vicinity of the opening, in the middle of the length of the branch pipe, and in the vicinity of the closed end by welding or brazing. It can be firmly fixed to the housing.
According to the present invention, since the branch member is formed by pressing a flat plate, almost all the members of the muffler can be realized by pressing, welding, and brazing.
According to the present invention, the exhaust port is provided on the front housing side, and the exhaust gas is discharged downward on the side opposite to the engine. Therefore, when the engine working machine with the muffler of the present invention is realized, the worker Against the exhaust gas.
According to the present invention, since the engine working machine including the muffler according to any one of the claims is provided, an engine working machine capable of achieving a reduction in size and weight with high output and low noise can be realized.

  The above and other objects and novel features of the present invention will become apparent from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of an engine work machine 1 using an engine according to an embodiment of the present invention, and a part thereof is a cross-sectional view. 1 is a longitudinal sectional view of an engine 2 and a muffler 20 according to an embodiment of the present invention. It is a disassembled perspective view which shows the assembly structure of the muffler 20 of FIG. It is a disassembled perspective view which shows the assembly structure of the connection pipe line 21 of FIG. It is a perspective view which shows the state after the assembly of the connection pipe line 21 of FIG. It is a perspective view which shows the shape of the front housing 41 of FIG. It is a perspective view which shows the state which attached the connecting pipe line 21 to the front housing 41 of FIG. FIG. 8 is an enlarged cross-sectional view near the center of FIG. 7. It is a perspective view which shows the state which attached the partition plate 35 to the state of FIG. It is a fragmentary perspective view which shows the shape of the cutout part 41c vicinity at the time of attaching the partition plate 35 like FIG. It is a fragmentary sectional view of the cutout part 41c shown in FIG. It is a perspective view which shows the shape of the branch member 30 of FIG. It is a perspective view which shows the state after attaching the branch member 30 from the state of FIG. It is a perspective view which shows the shape on the opposite side (back side) of FIG. It is a perspective view which shows the state which attached the flange 27 to the state of FIG. It is a perspective view which shows the external appearance after completion of the assembly of the muffler 20 of FIG. It is a longitudinal cross-sectional view of the muffler 120 which concerns on the 2nd Example of this invention. It is a disassembled perspective view which shows the assembly structure of the muffler 120 of FIG. FIG. 18 is an exploded perspective view showing an assembly structure of the connection pipeline 121 and the branch pipeline 130 of FIG. 17. FIG. 18 is a perspective view showing the shape of the front housing 141 of FIG. 17. FIG. 18 is a perspective view illustrating a state in which a connection pipeline 121 and a branch pipeline 130 are attached to the front housing 141 of FIG. 17. FIG. 18 is a front view of the front housing 141 and the branch pipe line 130 of FIG. 17. It is sectional drawing of the AA part of FIG. It is sectional drawing of the BB part of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same portions are denoted by the same reference numerals, and repeated description is omitted. Further, in the present specification, the description will be made assuming that the front-rear, top-bottom, left-right directions are the directions shown in the drawing.

  FIG. 1 is a side view of an engine work machine 1 according to an embodiment of the present invention, and a part thereof is shown in a sectional view. The cross-sectional position is a position where the exhaust port is divided into two in the cylinder axis direction of the two-cycle engine, and the piston position indicates a top dead center state. In the present embodiment, the engine work machine 1 is an engine cutter in which an engine 2 of two cycles is mounted inside the engine cover 14, and an operator grips with one hand (mainly the left hand) on the front side of the engine cover 14. A handle portion 5 is provided near the rear end of the engine cover 14 so that an operator can hold it with one hand (mainly the right hand). In the engine 2, a piston 4 is disposed so as to be able to reciprocate inside a cylinder 3 attached to an upper portion of a crankcase 9, and the piston 4 is connected to a crankshaft 16 by a connecting rod. The cylinder 3 is manufactured, for example, by integral molding of an aluminum alloy, and is provided around the combustion chamber 6 formed by the cylinder 3 and the piston 4, and a plurality of fins for heat dissipation are provided on the outer peripheral side of the head portion and the cylindrical portion.

  A spark plug 7 is attached to the top of the cylinder 3. An exhaust port (exhaust port) 8 is formed at a part of the cylinder 3 where the opening is opened and closed by the piston 4, and a muffler 20 is attached to the front side of the exhaust port 8. Although not shown, two bolt holes (female screws) are formed near the left and right of the exhaust port 8, and the muffler 20 is directly fixed to the cylinder 3 based on two mounting bolts (not shown). A scavenging port (not shown) is formed in the cylinder 3, and a passage from the crank chamber to the cylinder 3 is formed by a scavenging passage (not shown). The cylinder 3 is further provided with an intake port 17, and a carburetor (not shown) is attached to the intake port 17 via an intake pipe. Since a known vaporizer can be used as the vaporizer (not shown), description thereof is omitted here.

  The engine working machine 1 according to the present embodiment is a so-called upright engine in which the cylinder 3 of the engine 2 is arranged in the vertical direction (vertical direction), and the exhaust port 8 is arranged to open from the engine 2 toward the front side. Is done. This front side means that it is on the front side of the surface passing through the cylinder axis and the crankshaft 16, and is also a direction toward the rotating blade 11 as a working member. Since the muffler 20 is directly attached near the exhaust port 8, the muffler 20 is located in the space between the engine 2 and the rotary blade 11. A wheel guard 12 is provided on the outer peripheral portion on the rear side of the rotating blade 11. A connection pipe line 21 having a predetermined length is provided inside the muffler 20, and the connection pipe line 21 is bent into a substantially U shape in a side view and opens into the expansion chamber 40.

  On the right side of the muffler 20 of the engine working machine 1, an arm 13 for supporting a mechanism for rotating the rotary blade 11 is located. Although not shown in FIG. 1, an ignition coil for supplying a high voltage current to the spark plug 7 is provided on the left side of the muffler 20. Therefore, the muffler 20 is disposed in a limited space in the left-right direction and in a limited space between the rotary blade 11 and the engine 2 in the front-rear direction. In the engine working machine 1, it is important to make the entire length compact. In particular, it is desirable to make the distance S between the cylinder axis of the engine 2 and the center of the rotary blade 11 in the front-rear direction as short as possible.

  FIG. 2 is a longitudinal sectional view of the engine 2 and the muffler 20 according to the embodiment of the present invention. The muffler 20 is mainly composed of a connection pipe line 21, a branch member 30, an expansion chamber 40 (first expansion chamber 40a and second expansion chamber 40b), and an exhaust outlet portion described later. The expansion chamber 40 is a closed space having a predetermined capacity defined by two metal housing members (the front housing 41 and the rear housing 51), and has a front expansion chamber (first expansion chamber 40a) in the inside thereof. ) And a rear expansion chamber (second expansion chamber 40b). The front housing 41 and the rear housing 51 are joined together by caulking at the outer edge portion of the joining surface. The front housing 41 and the rear housing 51 are manufactured by press working using SPCE (cold rolled steel sheet for deep drawing). The front housing 41 is shaped along the outer periphery of the wheel guard 12 (see FIG. 1), and the lower portion thickness (front / rear length) d4 is thicker than the upper portion thickness (front / rear length) d3. It is formed (long) and secures as much volume as possible in a limited space. Similarly, the shape of the rear housing 51 is made to conform to the outer peripheral shape of the engine 2, and the thickness (front / rear length) d2 of the lower portion is thicker (longer) than the thickness (front / rear length) d1 of the upper portion. )It is formed.

  Exhaust gas discharged from the exhaust port 8 of the engine 2 flows into a connection pipe line 21 formed in a substantially U-shape that is laterally viewed from the side. The connection line 21 connects the exhaust port 8 of the engine 2 and the inlet portion of the expansion chamber 40 (first expansion chamber 40a). The connection line 21 is separated from the engine 2 and is connected to the axis 8a of the exhaust port 8. The opening 21b is disposed so as to extend downward so as to be away from the extension line and to enter the internal space of the expansion chamber 40. The opening 21 b serves as an exhaust gas inlet to the expansion chamber 40. The connecting pipe line 21 has a shape along the inner wall shape of the front housing 41 and is mainly formed with two radii of curvature. A flange 27 is provided in the opening 21 a on the exhaust port 8 side of the connection pipe line 21. The flange 27 is an attachment member provided to fix the muffler 20 to the cylinder 3 of the engine 2 with two bolts (not shown). The muffler 20 is also fixed to the crankcase 9 by two bolts (not shown). In this specification, the screw and the bolt are not strictly distinguished from each other, but both are described as being almost agreed as the fastening member. However, if the fastening means is screwed using the male screw and the female screw, the screw But it can be bolts or other means. Further, the number and positions of the locations where the muffler 20 is fixed to the engine 2 may be set as appropriate according to various factors such as the size of the muffler 20, vibration characteristics, and assembly.

  As a series of cycles of the engine 2, the piston 4 rises toward the top dead center, and when fresh air (a mixture of fuel and air) is ignited by the spark plug 7 and explodes, the piston 4 descends from the top dead center. The exhaust port 8 communicates with the combustion chamber 6 and the combustion gas is discharged from the combustion chamber 6 to the outside of the engine 2 as indicated by an arrow 39a. Immediately after the exhaust port 8 is opened, the pressure in the combustion chamber 6 is high, so that the combustion gas flows from the exhaust port 8 into the connection line 21 and the branch line 31 as indicated by arrows 39b and 39j. At this time, a positive pressure wave comes out from the exhaust port 8, and most of the outflowing combustion gas passes through the connection pipe line 21 as indicated by arrows 39b to 39d. When the positive pressure wave passes through the far end (opening 21 b) of the connection pipe line 21 communicating with the expansion chamber 40, the negative pressure wave propagates from the expansion chamber toward the exhaust port 8, and enters the combustion chamber 6. Bring a lot of attention. Immediately before the exhaust port 8 is closed, a positive pressure wave returns from the expansion chamber 40 toward the exhaust port 8, a part enters the branch pipe 31, and the positive pressure wave returns to the exhaust port with a delay, thereby causing a new unburned new wave. The air is kept from being discharged from the combustion chamber 6. Here, when the length, volume, and shape of the connection pipe line 21 and the branch pipe line 31 are appropriately designed, immediately after the scavenging opening, the negative pressure wave inverted from the open end (opening 21b) of the connection pipe line 21 The exhaust port 8 becomes a negative pressure, and fresh air in the crankcase 9 can be effectively introduced into the combustion chamber 6 from the scavenging port, which can lead to higher output of the engine 2.

  When the scavenging port communicates with the combustion chamber 6, fresh air is supplied from the crankcase 9 to the combustion chamber 6. Then, when the piston 4 reaches the bottom dead center and then the piston 4 rises toward the top dead center, the communication between the scavenging port, the exhaust port 8 and the combustion chamber 6 is released, and the intake port 17 is connected to the crankcase. The fresh air flows into the crankcase 9 through the intake port 17 in communication with the inside of the crankcase 9. At the end of the scavenging port closing, in the vicinity of the exhaust closing port, a part of the propagation of the positive pressure wave from the expansion chamber 40 increases the pressure in the vicinity of the exhaust port 8, and the positive pressure wave that has flowed into the branch pipe 31 from the connection pipe 21 with a delay. As a result, the high pressure in the vicinity of the exhaust port 8 can be maintained. Thereby, it is possible to push back fresh air to be blown out from the exhaust port 8 to the combustion chamber 6 in the vicinity of the exhaust closing port, and it is possible to aim for cleaner exhaust gas and improved output.

  The expansion chamber 40 is provided with a predetermined internal space in order to achieve an effect of reducing the volume of exhaust gas, and is disposed in a limited space between the cylinder 3, the crankcase 9 and the connection pipe line 21. The interior of the expansion chamber 40 includes a first expansion chamber 40a defined between the central partition plate 35 and the rear housing 51, and a second expansion chamber defined between the central partition plate 35 and the front housing 41. Two chambers 40b are provided, and the exhaust gas flowing in from the connection pipe 21 as indicated by an arrow 39e flows as indicated by an arrow 39f while being expanded in the first expansion chamber 40a, and enters the partition plate 35 as indicated by an arrow 39g. It flows through the provided opening and flows into the second expansion chamber 40b. The exhaust gas flows downward in the second expansion chamber 40b as indicated by an arrow 39h, and is discharged to the outside of the muffler 20 as indicated by an arrow 39i through an exhaust pipe described later formed in the second expansion chamber 40b. Further, in order to maximize the exhaust volume reduction effect without impairing the exhaust pressure pulsation effect, the volume ratio of the first expansion chamber 40a and the second expansion chamber 40b is 4: 6 to 6: 4. The range can be set.

  In this embodiment, the connection pipe line 21 is provided inside the expansion chamber 40, mainly inside the second expansion chamber 40b, so as to contact the inner side (inner wall) of the expansion chamber 40. For this reason, the connecting pipe line 21 has a U-shaped shape having an open end toward the crankcase 9 when viewed from the side as shown in FIG. 2, and from the exhaust port 8 within a limited space. The length of the pipe line reaching the expansion chamber 40 can be ensured, and the exhaust effect can be enhanced. Since the connection pipe line 21 is connected so as to extend in the direction of the axis 8a of the exhaust port 8, the flow path resistance to the exhaust gas can be reduced as much as possible, and the exhaust pulsation effect can be sufficiently obtained. Further, a branch pipe 31 having one end closed and the other open end connected in the middle of the connection pipe 21. The branch pipe 31 is constituted by a space defined by the partition plate 35 and the branch member 30 and is provided to synchronize the pressure wave at the normal rotation speed of 8,000 rpm to 9,500 rpm and improve the output. Although the inside of the expansion chamber 40 has two compartments in the present embodiment, it may be divided into only one compartment or two or more compartments. A catalyst may be disposed inside the expansion chamber 40.

  FIG. 3 is an exploded perspective view showing the assembly structure of the muffler 20. In the muffler 20 of the present embodiment, the expansion chamber 40 (see FIG. 2) is configured by joining the front housing 41 and the rear housing 51 so that the recesses face each other. The rear housing 51 is manufactured using a plate material whose outer shape is slightly larger than that of the front housing 41, and the front housing 41 is bent by bending the outer edge portion 51 b of the rear housing 51 forward and sandwiching the outer peripheral edge of the front housing 41. The rear housing 51 is joined by crimping. When the front housing 41 and the rear housing 51 are caulked, a flat partition plate 35 is interposed between the expansion chamber 40 and the first expansion chamber (internal space of the rear housing 51) 40a. It was divided into a second expansion chamber (internal space of the front housing 41) 40b. An opening 51a and a through hole 35b are formed in a portion connected to the rear housing 51 and the exhaust port 8 of the partition plate 35, the connection pipe 21 is penetrated through the through hole 35b, and a flange 27 is provided in the opening 51a. The connection pipe line 21 is connected through this.

  The connecting pipe line 21 has a shape along the inner wall shape of the front housing 41, and is a pipe line that guides the exhaust gas from the exhaust port 8 into the first expansion chamber 40a through a predetermined path length by joining to the inner wall. The In this embodiment, it is referred to as a “pipe”, but it is not necessary to have a strict pipe, and it may be a tubular inflow passage (passage) having a surrounding partition wall. The connection pipe line 21 extends through the through hole 35c formed in the partition plate 35 into the first expansion chamber 40a, and the opening 21b opens in the first expansion chamber 40a. In this way, the connection pipe 21 is formed in a U shape so as to face the crankcase 9 side of the engine 2. Unlike the technique of Patent Document 1 in which this pipe line is arranged outside the housing, in this embodiment, the connection pipe line 21 is arranged on the inner side of the second expansion chamber 40b, whereby the second expansion chamber 40b by the front housing 41 is arranged. Can be increased to the limit as far as space permits. The front housing 41 side of the connection pipe line 21 is an opening 21c, and the connection pipe line 21 is attached to the inner side of the front housing 41 and joined so that the opening part 21c is closed. For this reason, it is possible to prevent the wall of the connection pipe line 21 and the inner wall of the front housing 41 from being doubled (contacted in parallel), thereby further improving the space efficiency and effectively preventing the generation of resonance noise.

  The partition plate 35 is manufactured by, for example, SPCC (cold rolled steel plate), and an opening 35a for flowing exhaust gas from the first expansion chamber 40a to the second expansion chamber 40b is formed in the center, and a connecting pipe line is formed above and below the opening 35a. Through-holes 35b and 35c are formed through which 21 penetrates. A bent portion 36 c is formed at a part of the peripheral edge of the through hole 35 c and is used for joining to the connection pipe line 21. Beads 37a, 37b, 37c, and 37d are provided on the planar portion of the partition plate 35 to improve the strength. The partition plate 35 is further provided with through holes 38 a and 38 b communicating with the through holes 43 c and 43 d of the front housing 41.

  A flange 27 is provided on the inlet side of the connection pipe 21, and collars 31 a and 31 b for passing through bolts that fix the muffler 20 to the cylinder 3 are attached to the flange 27. The opening 21b of the connection pipe line 21 is disposed so as to penetrate the through hole 35b of the partition plate 35, and is disposed so as to extend toward the first expansion chamber 40a. Note that the through hole 35c of the partition plate 35 is not limited to the through hole, and the connection pipe line 21 may be passed as a cutout portion in which the lower portion of the partition plate 35 is cut out. Furthermore, in the present embodiment, the connection pipe line 21 extends through the partition plate 35 and extends into the first expansion chamber 40 a, but the opening 21 b stops at a position where it coincides with the through hole of the partition plate 35. You may comprise as follows.

  The connecting pipe 21 is formed with an opening 21d as a branching portion, and the branch member 30 is connected thereto. The branch member 30 is a member obtained by bending a flat plate into a U shape by press molding, and further bending it into a U shape. The flow direction of the exhaust gas in the connection pipe 21 and the axis of the inlet of the branch pipe 31 are substantially the same. It arrange | positions so that it may orthogonally cross. In order to form the inlet of the branch pipe 31, an opening 41 d having a shape corresponding to the opening 21 d of the connection pipe 21 is formed in a part of the front housing 41. In this embodiment, in order to stably fix the connecting pipe 21 partition plate 35, a bent portion 22a is formed by bending a part thereof. The branch member 30 is attached to the front housing 41, and the gap is closed by brazing or the like, so that the branch pipe 31 is formed together with the partition plate 35. The end of the branch pipe line 31 located on the side opposite to the opening 41d is closed by a closing part 44. The closing part 44 is formed by deforming a part of the front housing 41 by pressing. The reason why the closing portion 44 is provided is that it is difficult to form the closing end portion by the branch member 30, and the closing portion 44 is closed by another method without providing the closing portion 44 on the front housing 41 side. You may comprise as follows.

  FIG. 4 is an exploded perspective view showing an assembly structure of the connection pipe line 21 of FIG. The connection pipe line 21 is manufactured by joining, for example, a central wall 22, a right wall 23, and a left wall 24 that are formed by bending a plate material by pressing. These are spot-welded to the central wall 22 at several locations of the right wall 23 and the left wall 24 for positioning, for example. Here, an adhesive, brazing, or the like may be used together as necessary. A bent portion 22 a for fixing to the partition plate 35 is formed in a part of the central wall 22. It should be noted here that an opening 21c (see FIG. 3) is formed on the front surface side of the connection pipe line 21, so that the part is cut out as shown by arrows 25 and 26. It is. In addition, as shown in FIG. 4, the connecting pipe 21 is divided into components. By forming the plate divided into three parts by welding or brazing, individual parts can be manufactured only by shallow drawing or bending. This is because productivity can be improved, and airtightness as a passage can be improved, and a pressure pulsation effect can be obtained with certainty.

  FIG. 5 is a perspective view of the shape of the connection pipe line 21 after assembly, as viewed from the cylinder 3 side of the engine 2. An opening 21a for connecting to the exhaust port 8 is formed above the connection pipe 21, and an opening 21b that opens into the first expansion chamber 40a is provided below. Here, the size of the opening 21a is approximately equal to the opening area of the exhaust port 8, but the opening 21b is configured so that its cross-sectional area is larger than that of the opening 21a. Is easier to return. Since the outer peripheral side of the connecting pipe 21 is joined to the partition wall (= the inner wall of the front housing 41) of the second expansion chamber 40b, the outer peripheral side has a size and shape that matches the inner wall of the front housing 41. As can be seen from FIG. 4, an opening is formed on the outer peripheral side of the connection pipe line 21, but the inner peripheral side of the connection pipe line 21 is a partition wall.

  FIG. 6 is a perspective view showing the shape of the front housing 41. The front housing 41 has a function of defining the second expansion chamber 40b, a function of forming a screw boss portion for fixing a bolt for fixing the muffler 20 to the cylinder 3, and sealing the connection pipe line 21 by contacting the outer peripheral side of the connection pipe line 21. A function of providing an exhaust port 41a for exhausting the exhaust gas in the second expansion chamber, and a function of providing a screw hole for fixing the muffler 20 to the crankcase 9 or the cover of the engine working machine 1 or the like. The present embodiment further has a function of forming a branch pipe line, and a U-shaped cutout 41c for connecting the branch member 30 is formed. The front housing 41 is formed with a concave recess for defining the second expansion chamber 40b, and screw holes 43a and 43b for penetrating bolts for fixing the muffler 20 to the cylinder 3 are formed above the recess. . In the vicinity where the screw holes 43a and 43b are formed, cube-shaped or rectangular parallelepiped projecting portions 45 and 46 projecting forward are formed, and the projecting portions serve as screw boss portions to hold the collars 31a and 31b (see FIG. 3) and Become. The protrusions 45 and 46 are formed with beads 45b and 46b for improving the strength. Since the protrusions 45 and 46 viewed from the second combustion chamber side are in a hollow state, the inside serves to increase the volume of the second expansion chamber 40b.

  In the vicinity of the center of the front housing 41, a mounting portion 41b having a contour that fits the connecting pipe line 21 is formed. The attachment portion 41b is a step-like portion that is elongated from the top to the bottom and protrudes from the inside to the outside, and part of the attachment portion 41b is improved in strength by two beads 48a extending in the vertical direction. Yes. Further, three beads 48b and 48c extending in the front-rear direction are formed on the side of the mounting portion 41b, so that the strength of the front housing 41 is improved. In the vicinity of the lower side of the front housing 41, an exhaust port 41a is provided. A flange 49 is provided around the exhaust port 41a. The front housing 41 is sandwiched between the flange 49 and the exhaust pipe 60 (see FIG. 3), and the parts are fixed by fastening with screws (not shown). In the vicinity of the exhaust port 41a, a projecting portion 47 projecting from the engine 2 to the opposite side (in this case, forward) is used to increase the volume of the second expansion chamber 40b. In this embodiment, the outer edge portion of the front housing 41 is caulked by the outer edge portion 51b of the rear housing 51, so that all the outer edges are formed as flat ribs 41e. Through holes 43c and 43d for fixing the muffler 20 to a screw hole (not shown) of the crankcase with a bolt (not shown) are formed in a part of the rib 41e.

  FIG. 7 is a perspective view showing a state in which the connection pipe line 21 is attached to the front housing 41. The front housing 41 and the connection pipe line 21 are firmly joined by providing a brazing material on the outer peripheral portion of the front housing 41 that is in contact with the connection pipe line 21 and brazing. A method of joining using this brazing material is known, and the connection pipe line 21 is connected to the front housing 41 by using an alloy having a melting point lower than that of a member to be joined (the front housing 41 or the connection pipe line 21 as a base material). Can be joined well without gaps. Note that these fixings are not limited to brazing, but may be performed by using one or a plurality of known joining methods such as soldering, whole welding, spot welding, adhesive, and screw tightening. As can be understood from FIG. 7, since the connection pipe line 21 is provided inside the front housing 41, even if an exhaust gas leaks from the vicinity of the joint, it will leak into the second expansion chamber 40 b. In addition, the influence on the outside can be greatly suppressed. Further, since the joint portion of the connection pipe line 21 is not exposed to the outside of the muffler 20 in the front housing 41, it is possible to form a muffler that has a clean appearance from the outside and has no fear of exhaust leakage. Furthermore, since it is possible to expand the volume of the second expansion chamber as much as possible by providing protrusions 45, 46, and 47 around the connection pipe line 21, a large expansion chamber can be realized in a limited space. It was.

  FIG. 8 is an enlarged cross-sectional view around the center of FIG. It will be understood from this cross-sectional view that the connecting pipe 21 is joined to the inner wall portion of the front housing 41 to form a passage from the exhaust port 8 to the first expansion chamber 40a. The joint location where the brazing material (paste) between the front housing 41 and the right wall 23 and the left wall 24 is applied may be a location facing each other and its surroundings, and a known brazing method so as not to cause exhaust leakage. May be used so as not to cause leakage of the exhaust gas flow.

  FIG. 9 is a perspective view showing a state in which the partition plate 35 is attached to the state of FIG. In this embodiment, a bent portion 36c is provided at a part of the periphery of the through hole 35c of the partition plate 35, and the connection pipe line 21 is spot-welded on the bent portion 36c. Similarly, a bent portion 36b (described later) is also provided at a part of the peripheral edge on the through hole 35b side of the partition plate 35, and the bent portion is a spot with the bent portion 22a (see FIG. 5) of the connection pipe line 21. Welded. The partition plate 35 is provided with through holes 38 a and 38 b communicating with the through holes 43 c and 43 d of the front housing 41.

  FIG. 10 is a partial perspective view showing the shape near the cutout 41c when the partition plate 35 is attached as shown in FIG. In this embodiment, the branch member 30 is brazed to the cutout portion 41c from the state shown in FIG. Since the cut-out portion 41c is formed by press working, burring processing is performed in which the peripheral edge rises forward. For this reason, the joining area with the peripheral part of the branch member 30 increases, and the three of the branch member 30, the front housing 41, and the partition plate 35 can be joined without a gap by brazing. In addition, the rising part by the burring process is not provided in the vicinity of the opening 41d (in the vicinity of the arrow 55), but this prevents interference with the press part forming the expansion chamber and facilitates securing of the sealing property. It is to do.

  FIG. 11 is a partial cross-sectional view of the cutout 41c shown in FIG. The state of the burring process of the cutout portion 41c will be understood from the drawing. Since the connecting pipe line 21 is always exposed to vibration during operation of the engine 2, it is preferable to fix the branch member 30 and the partition plate 35 by welding, brazing, or the like. Can be firmly fixed. FIG. 12 is a perspective view showing the shape of the branch member 30. The branch member 30 is manufactured by pressing a metal plate (for example, SPCC) into a U-shape by pressing, and further bending it into a U-shape, and is joined to a flat partition plate 35. A branch pipe 31 is formed. The end 30a of the branch member 30 is firmly joined to the openings 41d and 21d. This joining is also performed by brazing. The other end 30 b of the branch member 30 is joined to the closing portion 44 of the front housing 41. The branch member 30 is formed with a bent portion 30c and is fixed by spot welding near the front housing 41 and the arrow 56 in FIG. Further, the branch member 30 is provided with a step portion 30d so that the positioning and the sealing performance can be easily secured when the branch member 30 is attached to the front housing 41. Thus, since the branch member 30 is composed of a separate part from the front housing 41, the shape of the front housing 41 is less likely to be restricted as compared to the case where the branch pipe line 31 is formed by pressing, A relatively large bending and a complicated shape can be realized in a narrow region. In this embodiment, the cutout portion 41c is arranged along the vicinity of the outer edge of the front housing 41, so that the branch conduit 31 having a large effective length can be formed within a limited installation area.

  FIG. 13 is a perspective view showing a state after the branch member 30 is attached by brazing from the state of FIG. As can be understood from this figure, since the branch pipe using the branch member 30 is formed in a U shape on the upper portion of the front housing 41, the length of the branch pipe is increased in a limited space. be able to. Since the branch pipe extends in a direction that is substantially perpendicular to the exhaust gas outflow direction at the branch portion (opening 41d), the branch pipe is disposed on the joint surface between the front housing 41 and the partition plate 35. Space efficiency is very good. Furthermore, since the protruding portion 45 is provided inside the U-shaped branch pipe, and the protruding portion 46 is provided near the outside, a mounting position of the boss seat for fixing the muffler 20 with a bolt is secured. At the same time, the capacity of the second expansion chamber 40b could be greatly increased.

  FIG. 14 is a perspective view showing the shape on the opposite side (rear side) of FIG. A bent portion 36 b formed at a part of the peripheral edge of the through hole 35 b of the partition plate 35 is spot welded to the connection pipe line 21. Further, collars 31 a and 31 b for penetrating bolts (not shown) are provided on both the left and right sides of the connection pipe line 21. Next, a brazing material (paste) is applied to the periphery of the opening 21a in the state shown in FIG. FIG. 15 is a perspective view showing a state in which the flange 27 is attached to the state of FIG. Positioning with respect to the collars 31 a and 31 b is performed by through holes 27 a and 27 b provided in the flange 27. By providing the flange 27 in this manner, the muffler 20 can be easily fastened and fixed to the cylinder 3, and sealing can be ensured and the connection pipe 21 can be prevented from being damaged due to vibration of the engine 2. Thus, after assembling into the procedure of FIGS. 4-15, these assembled parts are put in a furnace and brazing is performed.

  When the brazing operation is finished, the rear housing 51 is attached to the front housing 41 and the peripheral edge portion is crimped to complete the assembly of the muffler 20. FIG. 16 is a perspective view showing an appearance after the assembly of the muffler 20 of FIG. 2 is completed. In order to understand the shape of the rear housing 51 in FIG. 16, a device for enlarging the first expansion chamber in a limited space has been devised, and the convex portion 53 (from the inner side toward the rear side or the engine side) is made. The convex portion 54 of the lower portion is formed so as to protrude rearward along the outer edge of the crankcase 9. The rear housing 51 is also provided with a plurality of beads 55a to 55e extending in the vertical or horizontal direction in order to increase the strength. The rear housing 51 has screw holes 52 a and 52 b for fixing to the cylinder 3 and through holes 52 d for fixing to the crankcase 9 corresponding to the front housing 41.

  FIG. 17 is a longitudinal sectional view of a muffler 120 according to another embodiment of the present invention. As in the embodiment of FIG. 2, the muffler 120 is mainly composed of a connection pipe 121, a branch pipe 130, an expansion chamber 140 (first expansion chamber 140a and second expansion chamber 140b), and an exhaust outlet portion to be described later. The The expansion chamber 140 is a closed space having a predetermined volume defined by two metal housing members (the front housing 141 and the rear housing 151), and has a front expansion chamber (second expansion chamber 140b) in the closed space. ) And a rear expansion chamber (first expansion chamber 140a). The first expansion chamber 140a and the second expansion chamber 140b are partitioned by a partition plate 135. The volume ratio of the first expansion chamber 140a and the second expansion chamber 140b can be set to about the first expansion chamber: the second expansion chamber = 3: 7 to 7: 3, and in particular, the volume of the first expansion chamber 140a. Is preferably larger than the volume of the second expansion chamber 140b. Exhaust gas that has flowed into the first expansion chamber 140a through the connecting pipe 121 passes from the first expansion chamber 140a into the second expansion chamber 140b through the opening 135a formed slightly above the center of the partition plate 135. Inflow.

  The material of the front housing 141 and the rear housing 151 and the point manufactured by press working are the same as in the first embodiment. The shape of the front housing 141 is a shape that follows the outer peripheral shape of the wheel guard 12 (see FIG. 1), and the thickness (longitudinal length) of the lower portion is larger (longer) than the thickness (longitudinal length) of the upper portion. )It is formed. Similarly, the rear housing 151 has a shape that follows the outer peripheral shape of the engine 2, and the lower portion thickness (front / rear length) is made thicker (longer) than the upper portion thickness (front / rear length). Is done. The front housing 141 and the rear housing 151 are joined by caulking at the outer edge portion of the joining surface so as to sandwich the partition plate 135.

  The shape of the connection pipe line 121 is formed in a substantially U-shape that is lateral when viewed from the left side or the right side, and the outer wall portion on the front side of the connection pipe line 121 is shaped along the shape of the inner wall of the front housing 141. The front side surface of the connection pipe 121 is formed so as to be in close contact with the inner wall of the front housing 141. Here, close contact is made from the vicinity of the branch portions (121d, 130a, 141d) of the branch pipeline 130 to the vicinity of the arrow 126b near the caulking portion below the arrow 126a. A flange 127 is provided at the end connected to the exhaust port. An opening 121b is formed at the end of the connecting pipe 121 on the side away from the exhaust port, and the opening 121b is positioned so as to enter the internal space of the first expansion chamber 140a. The opening 121 b serves as an exhaust gas inlet to the expansion chamber 140. Although not provided in the present embodiment, a catalyst device can be incorporated in the muffler 120. Various positions for incorporating the catalyst device are conceivable. For example, if the catalyst device is incorporated at the position of the dotted line 125, the high temperature exhaust gas after passing through the catalyst does not directly hit the front housing 141, and therefore the front housing 141 exposed directly to the outside. Can be effectively prevented from heating. In addition, if a catalyst device is incorporated when manufacturing the connecting pipe 121, it is not necessary to change the assembly method thereafter, so that an increase in manufacturing cost can be suppressed.

  18 is an exploded perspective view showing an assembly structure of the muffler 120 of FIG. The muffler 120 of this embodiment is joined by crimping the front housing 141 and the rear housing 151 by bending the outer periphery of the front housing 141 so as to sandwich the outer periphery. When the front housing 141 and the rear housing 151 are caulked, a flat partition plate 135 is interposed between the expansion chamber 140 and the first expansion chamber (internal space of the rear housing 151) 140a. It was divided into a second expansion chamber (internal space of the front housing 141) 140b. The front housing 141 and the rear housing 151 are manufactured by press working using SPCE. The front housing 141 is formed with a main container portion defining the second expansion chamber 140b by pressing, and a portion of the wall portion having a bead 142c extending in the vertical direction and a portion protruding in the front direction is formed at the front end portion. In the vicinity of the center, a vertically extending cutout 141c is formed. The cutout part 141c is completely closed by fixing the connecting pipe 121 by brazing. An opening 141d, which is a through hole for connecting the branch conduit 130, is formed in the upper portion of the main container portion. Screw holes 143a and 143b through which screws for fixing the muffler 120 pass are formed in the vicinity of the opening 141d. Protrusions 145a and 145c are formed in the vicinity of the screw holes 143a and 143b of the front housing 141 so as to hold down collars 128a and 128b described later and to secure a large internal volume. Further, a projecting portion 145 b for holding the branch conduit 130 is formed near the upper portion of the front housing 141. A protrusion 147 for attaching a flange 149 in which an exhaust port 149a is formed is formed near the lower side of the front housing. The protrusion 147 serves as a mounting base for the flange 149 and serves to secure as much volume as possible of the second expansion chamber 140b. The front housing 141 is formed with a plurality of beads 142a to 142e for increasing rigidity, and the vicinity of the outer peripheral edge is crimped by the rear housing 151, so that it is formed in a flat plate shape having a predetermined width.

  The branch pipe 130 is a branch passage provided to keep unburned fresh air from being discharged from the combustion chamber 6 and has a predetermined length, and the end opposite to the branch point is closed. Is done. The branch conduit 130 is formed in a substantially U-shape that is upside down when viewed from the front side, and has one end serving as an open end 130a and the other end serving as a closed end 130b. One side of the branch conduit 130 is fixed by brazing so that no gap is formed between the opening 141d and the opening 121d. A part of the branch pipe is welded or brazed to the projecting portions 145b and 145c. Here, by appropriately setting the length of the branch conduit 130 (the length in the axial direction of the tube), the synchronized rotation speed of the pulsation can be changed using the pressure pulsation effect of the exhaust gas. In this embodiment, the branch conduit 130 is formed in a substantially U shape because of the installation space, but the branch angle from the branch portion (substantially perpendicular to the exhaust gas outflow direction) is not limited to this shape. If it can be ensured, the shape of the branch pipe 130 itself can be set relatively arbitrarily.

  The connecting pipe 121 is formed in a U shape so that the upper side faces the crankcase 9 side of the engine 2. A part of the wall surface of the front housing 141 on the side of the connection pipeline 121 is a cutout portion 141c, and the cutout portion 141c is blocked by attaching or welding or brazing the connection pipeline 121 to the inside of the front housing 141. Configured to be. As described above, since the cutout portion 141c can be reliably welded or brazed, the connection pipe 121 and the front housing 141 can be firmly fixed, and the assembly efficiency can be improved and the reliability and durability can be improved. A flange 127 is provided on the inlet side of the connection pipe 121, and collars 128 a and 128 b for passing bolts that fix the muffler 120 to the cylinder 3 are attached to the flange 127. An opening 121d is formed in the connection pipe 121 so that the branch pipe 130 can be connected, and an opening 141d is formed in a part of the front housing 141 at the same position as the opening 121d.

  In the vicinity of the center of the partition plate 135, an opening 135a for allowing exhaust gas to flow from the first expansion chamber 140a to the second expansion chamber 140b is formed, and a flat plate portion formed at the upper portion of the front housing 141 at the upper portion. An opening 135b that penetrates 141b is formed, and an opening 135c that penetrates the opening 121b of the connection pipe 121 is formed in the lower part. The shape of the opening 135c is a through hole, but may be a shape in which the lower half of the partition plate 135 is cut out. Reinforcing ribs 135d and 135e for increasing rigidity are formed around the openings 135b and 135c, and screw holes 135f and 135g for fixing the muffler 120 are provided. These openings 135a to 135c, ribs 135d and 135e, and screw holes 135f and 135g are formed by pressing.

  The shape of the rear housing 151 is formed along the outer peripheral shape of the engine 2, and as much expansion chamber volume as possible is secured in a limited space. An opening 151a for allowing exhaust gas to pass through is formed in the upper portion of the rear housing 151, and a flat outer edge 151b is formed around the opening 151a. A muffler 120 is installed on each of the left and right sides of the opening 151a. Screw holes 152a and 152b for attachment to (see FIG. 2) are formed. Screw holes 152c and 152d are formed near the lower side of the rear housing 151. The rear housing 151 is also formed with a plurality of beads 155a to 155e for increasing rigidity, and is configured such that the outer edge portion 151b can be bent forward and the outer peripheral edge of the front housing 141 can be sandwiched.

  FIG. 19 is an exploded perspective view showing an assembly structure of the connection pipeline 121 and the branch pipeline 130. The connection pipeline 121 is a pipeline formed by joining the right wall 123 and the left wall 124. The right wall 123 and the left wall 124 are formed by pressing a metal such as SPCC, for example, and notches 123d and 124d for forming an opening 121d (see FIG. 18) are formed in the vicinity of the side provided in the exhaust port 8. It is formed. The outer edge portion parallel to the flow direction of the right wall 123 and the left wall 124 (the direction in which the exhaust gas flows), particularly a portion having a predetermined width, is shaped to spread outward in the radial direction, and the right wall 123 and the left wall 124 In this way, exhaust gas is prevented from leaking. These joining methods may be a known welding method such as arc welding or brazing, or other joining methods such as caulking. After joining the right wall 123 and the left wall 124 as indicated by the arrow 1, next, the flange 127 is attached as indicated by the arrow 2 on the side fixed to the exhaust port 8 (see FIG. 2) of the connection pipe 121. . The flange 127 is a fixing bracket for fixing the muffler 120 to the cylinder 3, and holes 127 a and 127 b for passing bolts are formed at both left and right ends.

  The assembly structure of the branch pipeline 130 is basically the same as that of the connection pipeline 121, and the pipeline is formed by joining the front wall 131 and the rear wall 132. The reason why the connecting pipe 121 is divided into two parts in this way is that the ease of welding and the opening 121d of the branch pipe 130 can be easily formed. The front wall 131 and the rear wall 132 are formed by, for example, metal stamping such as SPCC, and an opening end 130a (131a, 132a) is formed on the side connected to the opening 121d, and the opposite end is closed. The ends 130b (131b, 132b) are used. The outer edge portion of the branch pipe line 130 excluding the open ends 130a (131a, 132a) has a bent flange shape that spreads outward in the radial direction for facilitating joining. When the rear wall 132 is joined to the front wall 131 as indicated by an arrow circle 3, the opening end 130 a of the branch pipe 130 is then connected to the opening 121 d of the connection pipe 121 as indicated by an arrow 4. However, the connection of the circle 4 is made after the connection pipe 121 is fixed to the front housing 141 and after the opening 141d and the opening 121d of the front housing 141 are positioned concentrically. The outer peripheral edge of the opening 121d is burring formed into a convex shape, the opening end 130a of the branch pipe 130 is inserted into the opening 121d, and the gap is blocked by welding or brazing. A pipe line that effectively uses the exhaust pressure pulsation is formed.

  As described above, in the second embodiment, the branch line 130 is formed by joining the flat plates that are narrowed in a U shape so as to be symmetrical by press molding, and is independent of the front housing 141. Formed as. The direction in which the exhaust gas flows through the connecting pipe 121 and the axis of the inlet of the branch pipe 130 are arranged so as to be substantially orthogonal. In the second embodiment, the branch pipe line 130 is separated from the front housing 141 and is externally attached, so that the productivity can be improved and the airtightness as the passage is improved and the pressure pulsation effect is surely achieved. Can be obtained. Further, since the branch pipe 130 hardly comes into contact with the front housing 141 except for the opening end 130a and a partial joint portion, the cooling effect on the branch pipe 130 is enhanced, and the exhaust temperature is reduced. As a result, the length of the branch line 130 can be made shorter than the length of the branch line 31 of the first embodiment. Note that the manufacturing method of the branch pipe 130 is not limited to the method shown in FIG. 19, but is formed by bending a cylindrical pipe, and welding one end side to the opening 141 d of the front housing 141 and the other end side. May be manufactured in a closed manner.

  FIG. 20 is a perspective view of the front housing 141 (however, it is a slightly oblique view and can be said to be a front view). The front housing 141 is manufactured by press working, and a plurality of beads 142a to 142e are formed to increase the rigidity while reducing the weight, and the vicinity of the outer peripheral edge is caulked by the rear housing 151 and thus has a predetermined width. It is formed in a flat plate shape. Also, a protrusion 145b for holding the branch conduit 130, protrusions 145a and 145c for holding the collars 128a and 128b, and a protrusion 147 for holding the flange 149 (see FIG. 18) are shown. The The projecting portion 147 is formed with an exhaust port 141a for exhausting exhaust gas, and screw holes 147a and 147b for screwing the flange 149 are formed in the vicinity of the exhaust port 141a.

  FIG. 21 is a perspective view of the front housing 141 from another angle. The front housing 141 is formed with a protruding portion 145 b that is close to the outer wall surface of the branch pipe 130 when the branch pipe 130 is attached to the connection pipe 121. The protrusion protruding forward from the front housing 141 includes a portion adjacent to the insertion portion of the connection pipe 121 and the branch pipe (protrusion 145a), and a vicinity of the center of the length of the branch pipe 130 (protrusion 145b). ), In the vicinity of the closed end 130b (protrusion 145c) of the branch conduit 130. In the vicinity of the upper side of the branch pipeline 130, the projecting portion 145 of the front housing 141 and the branch pipeline 130 are partially welded, so that the branch pipeline 130 can be stably fixed to the front housing 141.

  FIG. 22 is a front view of the front housing 141 and shows a state in which the branch conduit 130 is attached. The cutout portion 141c of the front housing 141 is formed to be long in the axial direction. However, the entire outer edge portion of the cutout portion 141c is brazed continuously so that there is no gap between the connection pipe 121 and the welded portion 122 indicated by a thick line. By doing so, the connection pipe line 121 can be firmly fixed to the front housing 141. In addition, since this brazing operation can be performed from the outside of the front housing 141, the workability is good. A flange 149 for forming an exhaust port 149a is attached to the protruding portion 147 of the front housing 141 by screwing or riveting.

  23 is a cross-sectional view taken along the line AA in FIG. From this figure, the connection structure of the front wall 131 and the rear wall 132 of the branch pipe 130 and the connection structure of the front housing 141, the partition plate 135, and the rear housing 151 will be understood. The projecting shape of the projecting portion 145b toward the front side is a shape along the outer peripheral surface of the branch conduit 130 as shown by the arrow 168, and a part of the projecting portion 145b and the branch conduit 130 are fixed by welding. In the figure, a weld bead 148b is shown. The length of the welded portion in the weld bead 148b (the length parallel to the axial direction of the branch conduit 130) may be relatively short, for example, less than 1.0 cm.

  24 is a cross-sectional view taken along the line BB in FIG. Similarly, the branch pipe 130 and the protruding portion 145c of the front housing 141 are fixed by welding. In the figure, a weld bead 148c is shown. The length of the weld bead (the length parallel to the axial direction of the branch conduit 130) may be about 0.5 to 3 cm.

  As described above, according to the second embodiment, the connecting pipe 121 can be configured as an independent pipe and can be firmly fixed by welding from the outside using the cutout portion 141c of the front housing 141. Further, the branch pipe 130 is formed as a pipe independent of the front housing 141 and the connection pipe 121, and the branch pipe 130 is located near the center of the U-shaped pipe as shown in FIGS. And one point near the closed end 130b are fixed by welding. With these structures, the connection pipeline 121 and the branch pipeline 130 can vibrate in the same vibration mode as that of the front housing 141, so that damage, dropout, and the like due to vibration during engine operation can be prevented. Usually, if the branch pipe 130 is configured independently, vibration is likely to increase. However, in the second embodiment, the welding area in the vicinity of the closed end 130b of the branch pipe 130 (the vicinity shown in FIG. 24) is set to other locations ( Since it is configured to be larger than the welding area of the portion shown in FIG. 23, vibration can be effectively reduced.

  As described above, according to the embodiments of the present invention, the expansion chambers 40 and 140 can be secured large even in an engine work machine that is easily restricted by the external shape of the work equipment, and the external appearance can be achieved without impairing the effect of pressure pulsation. We realized a muffler with a smaller size and an engine working machine using it. In particular, engine cutters that cut concrete, etc. have an arm for holding a power guard for rotating the wheel guard and blade around the muffler, and the height, width, and depth of the muffler expansion chamber are limited. In spite of this, the expansion chambers 40 and 140 can be secured large, the length of the passage (pipe) connecting the exhaust port and the expansion chamber can be sufficiently secured, and the effect of low exhaust gas and high output due to pressure pulsation. Could get. Furthermore, if the expansion chambers 40 and 140 are made common, it is easy to change the tuned rotation speed of the pulsation only by changing the lengths and cross-sectional areas of the connection pipelines 21 and 121 and the branch pipelines 31 and 130. Thus, since it can be easily applied to different displacements, a wide variety of expansion chamber mufflers can be easily manufactured.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, an example of an engine cutter that cuts concrete or the like has been described as an example of an engine work machine. It is also possible to do. Further, the tip tool mounted on the engine working machine is not limited to the rotary blade, and various known tools and operating members can be used.

DESCRIPTION OF SYMBOLS 1 Engine working machine 2 Engine 3 Cylinder 4 Piston 5 Handle part 6 Combustion chamber 7 Spark plug 8 Exhaust port 8a Axis 9 Crankcase 10 Handle 11 Rotating blade 12 Wheel guard 13 Arm 14 Engine cover 16 Crankshaft 17 Intake port 20 Muffler 21 Connection Pipe 21a Opening 21b Opening (expansion chamber inlet) 21c, 21d Opening 22 Central wall 22a Bending part 23 Right wall 24 Left wall 27 Flange 27a, 27b Through hole 30 Branch member 30a, 30b End 30c Bending Part 30d Step part 31 Branch pipe 31a, 31b Collar 35 Partition plate 35a Opening part 35b, 35c Through hole 36b, 36c Bending part 37a-37d Bead 38a, 38b Through hole 39a-39j Arrow (flow of exhaust gas) 40 Tension chamber 40a First expansion chamber 40b Second expansion chamber 41 Front housing 41a Exhaust port 41b Mounting portion 41c Cutout portion 41d Opening portion 41e Rib 43a, 43b Screw hole 43c, 43d Through hole 44 Closure portion 45, 46 Protruding portion 45b, 46b Bead 47 Protruding part 48a, 48b, 48c Bead 49 Flange 51 Rear housing 51a Opening part 51b Outer edge part 52a, 52b Screw hole 52c, 52d Through hole 53, 54 Convex part 55a-55e Bead 60 Exhaust pipe 120 Muffler 121 Connection pipe line 121b Opening part 121d Opening part 122 Welding part 123 Right wall 123d Notch part 124 Left wall 125 Dotted line 127 Flange 127a Hole 128a, 128b Collar 130 Branch pipe line 130a Open end 130b Closed end 131 Front wall 132 Rear wall 13 5 Partition plate 135a-135c Opening part 135d Rib 135f, 135g Screw hole 140 Expansion chamber 140a First expansion chamber 140b Second expansion chamber 141 Front housing 141a Exhaust port 141b Flat plate part 141c Cutout part 141d Opening part 142a-142e Bead 143a Screw Hole 145, 145a to 145c Protruding part 147 Protruding part 147a Screw hole 148b, 148c Welding bead 149 Flange 149a Exhaust port 151 Rear housing 151a Opening part 151b Outer edge part 152a to 152d Screw hole 155a Bead

Claims (22)

  A muffler having a front housing and a rear housing constituting the outer wall of the expansion chamber, and fixed to an engine cylinder, the rear housing having an opening connected to an exhaust port formed in the cylinder. A muffler characterized in that a connecting pipe line that is piped along the inner wall of the front housing from the opening and opens into the expansion chamber is provided.   The muffler according to claim 1, wherein the connection pipe is formed in a substantially U shape so that an end portion that opens to the expansion chamber faces the crankcase side of the engine.   The partition plate is provided between the front housing and the rear housing, and the expansion chamber is divided into a first expansion chamber on the rear housing side and a second expansion chamber on the front housing side. Scarf.   The said partition plate is provided with the opening part from said 1st expansion chamber to said 2nd expansion chamber, and the through-hole or notch part which penetrates the said connection pipe line. Scarf.   The muffler according to claim 3 or 4, wherein the volume of the first expansion chamber is larger than the volume of the second expansion chamber.   A part of the surface of the connection pipe line facing the inner wall of the front housing is opened, and the opening is closed by fixing the connection pipe line so that the opening contacts the inner wall of the front housing. The muffler as described in any one of Claims 1-5 characterized by the above-mentioned.   A part of the front housing facing the connection pipe line is open, and the opening is closed by fixing the connection pipe line so as to contact an inner wall of the front housing. The muffler according to any one of 5.   The muffler according to claim 7, wherein a flange is connected to the connection pipe, and the flange is fixed to the cylinder with a screw so as to be in contact with the rear housing.   The branch pipe is provided in the middle of the connection pipe, and a branch pipe having one end connected to the branch and closed at the other end is formed in the branch. The muffler as described in any one.   The muffler according to claim 9, wherein the branch pipe is piped along a dividing surface of the front housing and the rear housing.   The muffler according to claim 9 or 10, wherein the branch pipe is formed by joining a curved branch member to a curved cutout formed in the front housing.   12. The branch pipe is a convex member that follows the shape of the cutout portion, and the front housing is formed with a closing portion that closes the other end of the branch pipe. The muffler described in.   The muffler according to claim 11 or 12, wherein burring is made around a cutout portion of the front housing, and the branch member is held by the burring.   The muffler according to claim 9, wherein the branch pipe is an independent pipe and is connected to the branch portion.   The muffler according to claim 14, wherein the branch pipe is disposed at a predetermined distance from the front housing and the rear housing except for the branch portion.   The muffler according to claim 14 or 15, wherein the branch pipe is formed by joining members divided by a plane parallel to the axial direction.   The muffler according to claim 9 or 14, wherein a convex portion for holding the branch conduit is formed in the front housing, and the convex portion and the branch conduit are fixed.   18. The muffler according to claim 17, wherein the projecting portion and the branch pipe are fixed at one or more places except for the vicinity of a branch portion of the branch pipe with the connection pipe.   The muffler according to claim 17 or 18, wherein the protrusion and the branch pipe are fixed by welding or brazing.   The muffler according to any one of claims 9 to 19, wherein the branch member is formed by pressing a flat plate.   21. The muffler according to any one of claims 1 to 20, wherein an exhaust port is provided on the front housing side, and exhaust gas is discharged toward a lower side opposite to the engine.   An engine working machine comprising the muffler according to any one of claims 1 to 21.

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